High soil sodicity and alkalinity cause transient salinity in south-western Australia

Abstract

Transient salinity associated with increased dispersion of clays is arguably one of the most economically important soil constraints in Australia because it occurs on land that is regularly cropped. However, this issue is rarely studied. This paper examines the occurrence of transient salinity on agricultural land in the south-west of Western Australia and the factors causing it. We analysed four soil datasets from the region, collected at scales varying from the entire south-west to a single paddock. A variety of soil parameters were correlated with increased electrical conductivity (EC1:5). The most significant relationships were invariably with measures of exchangeable sodium (Na+; 53–85% of variance accounted for), and this factor appears to be most responsible for transient salinity. Another parameter correlated with increased EC1:5 was alkalinity. This has been associated with the increased dispersion of kaolinite and consequent decreases in soil hydraulic conductivity; kaolinite is the most common clay mineral in the south-west of Western Australia. Other factors correlated with increased EC1:5 were increasing clay, increasing depth in the soil profile and decreasing rainfall. These factors are environmental indicators of transient salinity. Affected soils might be ameliorated by application of agents to increase soil hydraulic conductivity, such as gypsum and/or elemental sulfur.